1. Field of the Invention
The present general inventive concept relates to a hybrid hard disk drive (HDD) having a hard disk and a non-volatile cache, and more particularly, to a method of controlling a hybrid HDD to permanently deactivate a non-volatile cache support mode by determining whether the limit in the use of a non-volatile cache is passed, and a recording medium and apparatus suitable for the control method.
2. Description of the Related Art
In a hybrid HDD, a non-volatile cache is additionally provided in addition to a typical HDD. The non-volatile cache is embodied by a flash memory. The hybrid HDD is advantageous in the following points as compared to a conventional HDD.
First, a booting time of an operating system (OS) may be reduced. Since files needed for the booting of the OS are copied to the non-volatile cache and used during booting, the booting time may be reduced. The typical HDD requires a time for a spindle motor to rotate up to a specified velocity during a power reset. However, since a host using the hybrid HDD may read the files needed for the booting of the OS from the non-volatile cache not located in the HDD, the booting time may be greatly reduced.
Second, a data access time may be reduced. Data to be used by the host using the hybrid HDD is simultaneously recorded on the non-volatile cache and a hard disk. When the data is read, the non-volatile cache is searched first. If appropriate data is found, the data is read from the non-volatile cache. Considering that recently recorded data is high-possibility accessed, the data access time may be reduced by using the non-volatile cache.
As it is widely known, the flash memory has a limit to how many times it may be used. Unlike a DRAM, writing to the flash memory involves first erasing a corresponding block, and the number of erasing operations is limited. The number of erasing operations of a currently used flash memory is limited to about 100,000.
FIG. 1 is a graph illustrating a relationship between an error of a flash memory and an erasure number limit. As illustrated in FIG. 1, when the erasure number of the flash memory exceeds the erasure limit number, an error, i.e., a data error during recording and reading, sharply increases. Thus, in the hybrid HDD, when the flash memory is used over the limited number of use, that is, when the non-volatile cache is used over an appropriate limit, the non-volatile memory may not be used further.